This invention relates to the partial oxidation of liquid hydrocarbonaceous fuels, including oxygen-containing hydrocarbonaceous fuels and slurries of solid carbonaceous fuels. More specifically, it relates to a pollution abatement process for the environmentally safe disposal of toxic CN-containing sludge produced during the treatment of water used to quench cool and/or scrub the hot effluent gas stream from a synthesis gas generator.
The hot effluent synthesis gas stream i.e., mixtures of H.sub.2 +CO from a free-flow non-catalytic partial oxidation gas generator may include trace amounts of HCN, i.e. 0.5 to 100 parts per million (PPM) by weight as well as entrained particulate matter such as soot, ash, slag, and bits of refractory. Water is most commonly used to quench cool and/or scrub the hot effluent gas stream from the reaction zone in order to remove the entrained matter. A portion of the HCN in the synthesis gas stream will be absorbed by the water in the quench and/or cooling zones, along with trace amounts of other water soluble impurities in the gas stream such as formates and halides.
Since large quantities of water are employed in the process for producing synthesis gas, reducing gas, or fuel gas by the partial oxidation of liquid hydrocarbonaceous fuels, including oxygen-containing hydrocarbonaceous fuels and slurries of solid carbonaceous fuels, it is important especially in arid locations to reclaim the quench and/or scrubbing water and to recycle them back to the gas quenching and/or scrubbing zones for reuse. In fact, for economic and environmental reasons, water recovery and upgrading, and recycling the upgraded water to the process have now become necessary.
U.S. Pat. No. 4,211,646, which is incorporated herein by reference, pertains to a method for the treatment of waste waters having toxic and corrosive properties due to the presence of cyanides, formates and halides. A toxic inorganic sludge and an upgraded waste water stream are produced by this method. No procedure is provided in U.S. Pat. No. 4,211,646 for safely disposing of concentrated toxic inorganic sludges.
Sludge disposal would represent a major operating cost in a plant producing synthesis gas from petroleum and coal feed. Free and complexed cyanides in the sludge must be destroyed before any sludge disposal system is environmentally acceptable. Complex cyanides are resistant to chemical destruction. Sunlight may break down complexed cyanide, but free cyanides are then released. If the inorganic sludge is landfarmed, contamination of ground water is a potential hazard.
These problems and others are eliminated by the subject process by which substantially all of the free and complexed cyanides in the inorganic sludge are destroyed in the reaction zone of the partial oxidation gas generator.